Fig. 3
Brief physiological activation of the CA3 C/A system initiates autonomous cell firing lasting minutes. a Nissl stained cross section of temporal hippocampus illustrates placement of stimulating (X) and recording (shaded) electrodes. A representative response (right) to a 10-pulse Θ train with stimulation artifacts (top left bar), where an individual fEPSP (from shaded zone) is shown on an expanded time scale below (Scale bars: y = 100 µV, x = 200 ms and 20 ms for top and bottom traces, respectively). b Representative sections of filtered (band pass 300–3000 Hz) extracellular recordings of pyramidal cell spiking during the baseline period (4 s), the Θ stimulation train (shaded blue, 2 s) and subsequent 4 s, as well as 1 min afterward (4 s). The detection threshold and those spikes counted during baseline are indicated with red shading and red dots, respectively. Note that firing frequency is increased following stimulation and this is maintained for ≥ 1 min (Scale bars: y = 100 µV, x = 1 s). c Scatter plot with unity line (dashed) illustrates the mean frequency before and 2 min after Θ stimulation for all cases (n = 23 slices; 57 trials). Mean frequency prestimulation and 2 min poststimulation were summarized for all cases (**p < 0.003, paired t-test pre versus post). d Bar graph summarizing the mean normalized (N) frequency (% control, CTRL) for each 10 s bin during the baseline period and for 4 min after Θ stimulation for 23 slices: group effects for bins were significant (p < 0.0001, prestimulation versus poststimulation). e Scatter plot with unity line (dashed) summarizes the mean frequency before and for the 2 min after Θ stimulation for positive cases only (n = 19 slices; 28 trials). Mean frequency pre- and 2 min post Θ stimulation were summarized for positive cases (***p < 0.0001 prestimulation versus poststimulation). f Bar graph summarizing the mean normalized frequency (% CTRL) for each 10 s bin during the baseline period and for the 4 min after Θ stimulation for positive cases (p < 0.0001 pre- versus post-stimulation). The blue bar describes mean frequency 8 min after the theta train
